7520 fuel pump problems

[jrchafin]

Hello all, have a Mahindra 7520 with 700 hrs on it, about 6 years old.

Using it the other day and I noticed a diesel fuel smell, found a leaky gasket in the bosch injector pump. The leak was on a gasket underneath a plate that was facing the engine block, so I had to take the pump off to fix the gasket. I have no idea why this started leaking, but it was running fine otherwise.

I removed the pump, and replaced the gasket as well at the other gaskets involved in the removal. I reinstalled it, and cracked the line that enters the pump, running through the filters and hand pump to the top of the injector pump. I hand pumped until fuel came to this point and then re tightened that line.

I knew the pump wasn't bled completely, but decided to try and start it. I cranked it and it ran great. put it at full throttle for a minute or so, no problems, no leak. I shut it down thinking I was done.

The next day it wouldn't run at all, just cranks and cranks with the starter, a little grey smoke coming from the exhaust. I figured I was air locked, so I removed the high pressure lines and tried to hand pump fuel through the pump. I have pumped that thing probably 50 times or more, and it feels like it's pumping, I can hear a hiss, but no fuel comes out of the high pressure ports.

What am I missing?

Thanks in advance.

 

[jrchafin]

Ok, got the pump bled, and got it running again, and it promptly started leaking again through the same gasket. Not just dripping here and there, but squirting out. It is coming from a gasket at the bottom right side of the pump toward the engine block, so it is hard to see exactly.

So now my question is, has anybody else had this problem? What's causing it to blow the gasket and what's the solution? Pump overhaul? UGH!

 

[SPYDERLK]

Ok, got the pump bled, and got it running again, and it promptly started leaking again through the same gasket. Not just dripping here and there, but squirting out. It is coming from a gasket at the bottom right side of the pump toward the engine block, so it is hard to see exactly.

So now my question is, has anybody else had this problem? What's causing it to blow the gasket and what's the solution? Pump overhaul? UGH!

Yes! ... Mine has it and Iv not fixed it. When I do I plan to put in some extra small bolts to limit clamping span and help squeeze the gasket uniformly. Is the rear steady bracket on your pump intact. I found mine had come loose -- maybe a contributor to failure? Any pointers you can give on pump removal and re timing?
larry

 

[jrchafin]

Any pointers you can give on pump removal and re timing?
larry

Yeah Larry. This pump is not difficult to deal with the timing. Just don't turn over the motor or spin the pump when they are separate. It bolts to the pump gear with a nut, keyway, and a tapered shaft. It's a bit of a wrestling match to get the tapered shaft to free up. The service manual talks of a "special tool" to remove it, but doesn't say anything else, like what the tool is or the part number. Brilliant. So I used a puller I had on hand as a pusher actually. I took some spare bolts and threaded them into the front cover plate bolt holes securing the puller in place, and then spun the center bolt of the puller tight against the shaft of the pump. This shaft has a dimple in it, so it works perfectly. Keep cranking on the puller bolt until enough tension builds that it pops the tapered shaft loose. When reinstalling just have to make sure the key on the shaft goes into the keyway of the pump gear.

 

[jrchafin]

Larry, I'm trying to decide if I should just get a new gasket from the mahindra dealer, or take the pump to be rebuilt. The gasket I put in the first time was just a basic gasket that I cut myself, not strong enough apparently. I guess my question boils down to this. Is it leaking because of too much pressure, ie: something wrong with the pump? Or is it just leaking and needs a new gasket? I've heard that the recent changes in diesel fuels are causing a lot of seals to fail, and maybe that's the cause.

 

[Navasot]

Have the pump rebuilt if your taking the time to have it off... no reason not to.... keep some good fuel treatment in the fuel and it will help lubricate the pump to keep this from happening... low sulfur sucks

 

[jrchafin]

Turns out mahindra doesn't supply any parts for this pump, according to my dealer. I found a company that will work on it, but would have to send it away and would cost big money. They sold me a new gasket for $12. Last one lasted 6 years, maybe this one will last another 6. Only takes me about 30 minutes to get the pump off, twice that to put it back on, so I think it's worth it to just replace the gasket and cross my fingers.

Larry, the business I found is just north of Lynchburg if you are in that area and want to have yours fixed up or get parts. valley fuel injection services, in madison heights, VA.

 

[SPYDERLK]

Yeah Larry. This pump is not difficult to deal with the timing. Just don't turn over the motor or spin the pump when they are separate. SNIP.

Thanks!

Larry, I'm trying to decide if I should just get a new gasket from the mahindra dealer, or take the pump to be rebuilt. The gasket I put in the first time was just a basic gasket that I cut myself, not strong enough apparently. I guess my question boils down to this. Is it leaking because of too much pressure, ie: something wrong with the pump? Or is it just leaking and needs a new gasket? I've heard that the recent changes in diesel fuels are causing a lot of seals to fail, and maybe that's the cause.

... But it is the gasket leaking, right? My impression w/o seeing it off is that there is a cover plate gasketed and bolted to the back side of the injector pump. I project that the bolted/clamp points on the plate are too far apart considering thickness/rigidity of the plate. The stock gasket works for a while - then leaks. Im guessing your home made replacement was not quite as compliant. :confused3:

-- All guesses, but when I take mine off Ill be looking at whether the span between clamp points is too much. Perhaps the center points of the spans have room for using a hi strength #4 or 6 capscrew to increase clamp force and make it more even.
larry

 

[jrchafin]

Thanks!

... But it is the gasket leaking, right?

Yep, definitely. But the cover plate is quite heavy, 1/4" thick, looks like grade 8 steel. Pretty beefy. Of course, additional bolts would give more even gasket compression, but I would worry about drilling and tapping into the pump. It's a pretty complicated mess in there, don't know how much room you would have to drill without messing something up. But sounds like a great fix.

 

[SPYDERLK]

Yep, definitely. But the cover plate is quite heavy, 1/4" thick, looks like grade 8 steel. Pretty beefy. Of course, additional bolts would give more even gasket compression, but I would worry about drilling and tapping into the pump. It's a pretty complicated mess in there, don't know how much room you would have to drill without messing something up. But sounds like a great fix.

Yeah. Ill have to size it up. Theres gotta be a way to actually fix it. I hate doing things twice. ... Was the rear brace point on your pump tight? Mine was loose - and may be the excuse.
larry

 

[jrchafin]

Yeah. Ill have to size it up. Theres gotta be a way to actually fix it. I hate doing things twice. ... Was the rear brace point on your pump tight? Mine was loose - and may be the excuse.
larry

My brace was tight. I don't think that would affect this gasket either way though.

 

[jrchafin]

So finally got time to put the new gasket in my fuel pump and re-install. It doesn't leak any more, but unfortunately doesn't run right either. I think there may be something wrong with the pump, but before I take it for a rebuild, I want to make sure I'm not missing something I can fix.

It's a VE type injection pump, which runs off a pump gear with a woodruff key. I did not crank the engine or move the location of the pump gear while the pump was off, and did not rotate the pump either. I was careful to align the key with the pump gear when I put the pump back on, and I've aligned the timing marks between the pump housing and the engine block. The engine runs, but very rough and has some strange behavior.

It starts and idles fairly well, but when I give it fuel, it doesn't do anything at first. Then, once I add enough throttle, the engine takes off and jumps up RPM, running fairly well, but still rough. It smokes gray intermittently, and even back fires some.

Controlling the throttle on the pump itself with my hand, the first inch or so of rotation doesn't have any effect in the engine, and then it suddenly takes off, jumping to 2000RPM or so. If I release the throttle it returns to a rough idle. So is something stuck inside the pump? I can't see any other explanation for why the throttle would be doing this.

Any advice on troubleshooting would be much appreciated.

 

[Navasot]

Try rolling the pump... loosen the bolts then turn it clockwise as much as possible then tighten back down.. it wont move much but should help

 

[Navasot]

Then I would let it run until it warms up and that will help bleed out any air in the system.

 

[jrchafin]

Try rolling the pump... loosen the bolts then turn it clockwise as much as possible then tighten back down.. it wont move much but should help

Doesn't that change the timing? I'd love to understand this system better. What do you think is going on? Why would moving it clockwise help?

 

[SPYDERLK]

Try rolling the pump... loosen the bolts then turn it clockwise as much as possible then tighten back down.. it wont move much but should help

Doesn't that change the timing? I'd love to understand this system better. What do you think is going on? Why would moving it clockwise help?

Yes it does, but I think theres not much range of movement so you cant change it much. Is sounds like your injection timing is out. Could that gear you extracted the pump from have possibly skipped a tooth while it was not being held engaged firmly by the pump shaft? ... That would do it I think - and theres not enuf rotational adjustment to make up for it AFAIK.
larry

 

[jrchafin]

Yes it does, but I think theres not much range of movement so you cant change it much. Is sounds like your injection timing is out. Could that gear you extracted the pump from have possibly skipped a tooth while it was not being held engaged firmly by the pump shaft? ... That would do it I think - and theres not enuf rotational adjustment to make up for it AFAIK.
larry

It does seem like that could be the problem Larry, but I can't imagine how that gear could skip a tooth. Any experienced folks out there know if that is possible on this engine? I rotated the pump clockwise as Nav suggested, and it did help, but is still not running right.

Jon

 

[jrchafin]

Ok. I'm waving the white flag. I got a day off today and pulled the pump back off, and the story just keeps getting worse. The nut that holds the pump shaft somehow worked it's way loose and was all the way off, but still sitting there when I took the front cover off. Unfortunately, the lock washer is nowhere to be seen. :ashamed:

I have determined there is no way to make the pump gear shift a tooth while it's still in it's housing, even with the pump off. Even went so far as to make a shaft that I bolted to the gear so I could shift it in every possible direction, and there is not enough play to disengage the teeth and shift them.

So I guess my problem must be the pump, which I will have rebuilt.

How much do I need to worry about that darn lockwasher??!! :duh:

 

[SPYDERLK]

There probably is nothing wrong with the pump. Any chance that loose/ missing nut caused enuf timing disruption to explain the ruf running? -- There is thrust due to drive on that helical gear that could cock it a little and change timing more than is intuitive. You could try reinstalling and see if its fixed. ... I would worry about the lockwasher, but probably irrationally. It likely fell out of the way and will stay there.
larry

 

[jrchafin]

I think the problem was air somewhere in the system. I pulled the pump again, replaced the fuel filters, checked all the fuel lines. i also used a boroscope to look inside the engine for that washer, and it's not in there. It's quite a large washer, and since it's a lock washer, it's pretty thick when not compressed, so there wasn't room for it to fall past the idler gear. Thankfully it's not in there. I just misplaced it somewhere. So I reinstalled everything, very carefully bled the lines and the pump. My plan was to do this and then bring it to a mechanic when it didn't run. But when I went to crank it, it fired up just like new. :cool2: